1. Field of the Invention
This invention relates generally to collapsible tubes used to contain and dispense fluids, and particularly to tubes having a seal of laminated material on the dispensing orifice of a prior art tube formed of a collapsible tube wall of laminate material welded to a plastic head portion.
Collapsible tubes are packages in tube form having a dispensing orifice at one end of a deformable tube. The tube is deformed and collapsed by squeezing so that the contents are forced out the orifice. Such tubes are used to contain toothpaste, pharmaceuticals, cosmetics, personal care products, artists' pigments, adhesives, sealants and caulking materials, greases and lubricants, foods and condiments, and many other products. Collapsible tubes generally have a screw cap closure.
2. Description of Related Art
a. Prior Art Collapsible Tubes
Collapsible tubes are formed of (1) metal alone or (2) plastic alone, or (3) a combination of a rigid plastic head portion and a deformable laminate tube body portion.
b. Method of Making Prior Art Collapsible Tubes
Metal tubes are formed by impact extrusion from metal slugs in a die cavity wherein a ram forces the metal into the tube shape.
Plastic tubes of, for instance, polyethylene, are injection molded into the desired shapes.
Laminate tubes consist of at least two parts; namely, (1) a rigid pure plastic head portion and (2) a tube body formed of a laminate of layers of plastic and metal foil, adhesively held together. The tube body is joined, in a separate step, to the molded plastic head by, for instance, radio frequency welding.
The tubes are filled through an open bottom. The tubes are then closed at the bottom, generally by a fold.
c. Prior Art Seals on Collapsible Tubes
Prior art collapsible tubes, particularly those formed of metal, often have a seal across the dispensing orifice of the tube. Seals are generally used when the tube contains medicinal products. The seal is pierced and deformed before the contents are discharged.
d. Method of Forming Prior Art Seals
Prior art seals have been formed in different ways, depending upon the material from which the tube is made.
In the invention disclosed in U.S. Pat. No. 4,938,818 incorporated by reference herein, a seal of laminate material is cut, positioned on the head dispensing orifice and held thereto, and then heat-sealed by a hot press to the orifice before the head is welded to the laminate tube wall. When the tube wall is subsequently assembled and welded by radio frequency to the head, a special heat sink is positioned adjacent the seal to avoid damage to the seal.
The laminate material from which the seal is made is in web form and positioned across the heat dispensing orifice. A seal is die cut from the web right over the orifice, whereupon it is held securely thereto by a vacuum applied through the bottom of the head through the orifice. A heat press is applied to the seal over the orifice and the thermoplastic layer in the seal laminate, which is adjacent to the thermoplastic lip of the dispensing orifice, melts the thermoplastic at the contact interface, after which the press is removed. The weld then cools, hardens and fuses the seal to the outlet.
The head is then assembled with the tube wall, which has been preformed in prior art fashion. In forming the tube wall, a continuous web of material is formed into a continuous tube and then welded as by radio frequency along the longitudinal seam. The continuous tube so formed is then cut into lengths corresponding to the collapsible tube lengths.
The tube lengths are then assembled individually on a mandrel and brought into position adjacent the tube heads and welded thereto by radio frequency.
A special heat sink is placed adjacent the seal to absorb heat generated by the weld operation, so there is no heat buildup in the laminate seal, which contains a metal foil layer.
The seal of laminate material is pierced to gain access to the tube contents, as shown for instance by a cap having a point, as shown in FIG. 10 of the '818 patent.
e. The U.S. Pat. No. 5,209,795.
In the invention disclosed in U.S. Pat. No. 5,209,795, incorporated by reference herein, means are provided to remove, rather than pierce, the seal formed by the method disclosed in U.S. Pat. No. 4,938,818 referred to above. The seal is provided with an integral tab. The tab is positioned on the neck of the tube perpendicular, or normal, to the plane of the seal across the tube opening, and hugs the neck without adhering thereto. The tab is easily lifted from the neck and pulled to peel the seal from its weld to the neck. The weld is a relatively strong one so that the strength of the laminate is far greater than that of a pure thin metal foil, and is utilized to transmit the necessary force to separate the bond, or weld, between the seal and the orifice formed by the heat press when the seal was applied.
The tab is formed integrally when the seal is cut as disclosed in the '818 patent, and bent and positioned along the neck when the seal is welded to the plastic head, again the manner taught in the '818 patent.